Characterization of a Novel Linezolid Resistance Gene optrA and Bacitracin Resistance Locus-Carrying Multiple Antibiotic Resistant Integrative and Conjugative Element ICE Ssu 1112S in Streptococccus Suis

Streptococcus suis strain 1112S was isolated from a diseased pig in a feedlot from Henan, China, in 2019. The isolate harbored a linezolid resistance gene . WGS data revealed that the gene was associated with a single copy ETAf IS , in tandem with (B) and (O), located in a novel 72,587 bp integrative and conjugative element (ICE). Notably, this novel element, designated ICE 1112S, also carried a novel bacitracin resistance locus. ICE 1112S could be excised from chromosome and transferred to the recipient strain S. suis P1/7 with a frequency of 5.9 × 10 transconjugants per donor cell. This study provided the first description of the coexistence of and a novel bacitracin locus on a multiple antibiotic resistant ICE and highlighted that ICE were major vehicle and contribute to the potential transfer of clinically relevant antibiotic resistance genes. Antimicrobial resistance (AMR) caused by the imprudent use of antimicrobials has become a global problem, which poses a serious threat to treatment of S. suis infection in pigs and humans. Importantly, AMR genes can horizontally spread among commensal organisms and pathogenic microbiota, thereby accelerating the dissemination of AMR determinants. These transfers are mainly mediated by mobile genetic elements, including ICEs. In S. suis, ICEs are the major vehicles that contribute to the natural transfers of AMR genes among different bacterial pathogens. However, ICEs that carry and bacitracin resistance locus are rarely investigated in S. suis isolates. Here, we investigated a S. suis isolate carrying an and a novel bacitracin resistance locus, which were co-located on a novel multiple antibiotic resistant ICE 1112S. Our study suggests that more research is needed to access the real significance of ICEs that horizontally spread clinical important resistance genes.